“CHEMISTRY OF LIFE”

ATOMIC STRUCTURE

ELEMENTS:

A SUBSTANCE THAT CAN NOT BE BROKEN DOWN INTO A SIMPLIER SUBSTANCE.

ELEMENTS CONSIST OF ONE TYPE OF ATOM. These four elements make up 96% of living things

c.

6

12.01

H1

1.00

O 8

15.99

N7

14.00

CARBON HYDROGEN OXYGEN NITROGEN

ATOMS:

aTOm: Greek for “unable to be cut”

Atoms are the building blocks of an element.

Atoms consist of three sub-atomic particles:– Protons: Positively

charged particles (p+)– NEUTRONS: Particles

with no charge (n°)– Electrons: negatively

charged particles (e-)

ATOMIC SYMBOLS:

Reading the atomic symbol

Atomic Number = The Number of Protons and Also the Number of Electrons

Atomic Mass = The Number of Protons Added to the Number of Neutrons

The small # isalways the Atomic Number& the larger # isalways the MassNumber !

Energy levels:

Protons (p+) and neutrons (n°)

Are located in the nucleusElectrons are located in Energy Orbitals outside of the nucleus

*Ist Energy Orbital= 2e-

*2nd Energy Orbital= 8e-

*3rd Energy Orbital= 8e-

*There is a “jumping” of e- between the 3rd & 4th Energy Level: We will fill using 2-8-8-18

OK….Let’s Practice!

96% of Your Body Is Made Up Of Four Elements on the Periodic Table:– C Carbon– H Hydrogen– O Oxygen– N Nitrogen Construct the Atomic Structure

Diagram for Each of these elements! We will Do the First one Together

ISOTOPES

Isotopes: atoms of the same element that have different # neutrons– EX: C-14

Isotopes are identified by their Mass Number (# protons + # neutrons)

All isotopes of the same element have the same chemical properties

Radioactive Isotopes

Radioactive Isotopes: isotopes with unstable nuclei and break down at a constant rate over time

Although possibly harmful, radioactive isotopes can be used to:– Determine age of rocks and fossils– Treat cancer– Kill food-spoiling bacteria

COMPOUNDS

Substance composed of 2 elements chemically combined.

Compounds form molecules. Examples:

NaCl (salt); C6H12O6 (sugar)

COVALENT BOND

Formed when 2 atoms share 1 or more pairs of electrons.

Prefix Co- means with/together.

Example: Hydrogen gas

Types of Covalent Bonds:

Single: 2 electrons shared

Double: 4 electrons shared

Triple (rare): 6 electrons shared

IONIC BONDS

Ion: an atom that has a positive or negative charge

Formed when Electrons are completely transferred from one atom to another.

IONIC BONDS (con’t)

Positive Ion: an atom that has lost a valence electron(s)– Also called cation

Negative Ion: an atom that has gained a valence electron(s)– Also called anion

For example, during the reaction of sodium with chlorine:

-Sodium (on the left) loses its one valence electron to chlorine (on the right),

-a positively charged sodium ion (left) and a negatively charged chlorine ion (right).

    resulting in

Solutions

Solution: mixture in which all components are distributed evenly

– Solute: substance being dissolved (ex: sugar)– Solvent: substance doing the dissolving (ex H2O)

– Concentration: amount solute per solvent Saturated soln.: can not dissolve any more solute

Mixture

A combination of substances in which the individual components keep their own properties

Example: – Sand & Sugar

When you stir the sand & sugar together, you can still tell the sand from the sugar.

Dissociation of Water

Water molecules can react to form ions

H2O → H+ + OH-

Or: Water → Hydrogen ions + Hydroxide

(Hydronium) ions.

Because the # of positive ions = # negative ions, water remains neutral

The pH Scale

Used to indicate the concentration of hydrogen ions (H+) in a solution

Scale ranges from 0-14

At pH of 7, the number of H+ ions is equal to the number of OH- ions

Pure water has a pH of 7 (“neutral”)

pH (con’t)

When pH of a solution is less than 7:– there are more H+ ions than OH- ions– These solutions are called Acidic

When pH of a solution is greater than 7:– there are less H+ ions than OH-ions– These solutions are called Basic

Acids

An acid is any compound that forms H+ ions when mixed in a solution

Turn Blue litmus paper → red

Acids have pH levels below 7

Bases

Base: a compound that forms OH- ions when mixed in a solution– Also called “Alkaline”

solutions

Turns red litmus paper → blue

Bases have pH levels greater than 7

Buffers

Buffers: compounds that help prevent sharp changes in pH within cells

Help protect living tissue by keeping pH within cells between 6.5 and 7.5